Perfected Grinding Machine and Grinding Method

ABSTRACT

A grinding machine for operative cylinders, of the type comprising a piece-holder head and a tailstock center between which an operative cylinder is positioned for being ground, includes a moving system associated with both the piece-holder head and the tailstock center to allow them to be moved along a common movement direction. A further object of the present invention relates to a grinding method.

FIELD OF THE INVENTION

The present invention relates to a perfected grinding machine for operative cylinders and a method for the grinding of said cylinders.

The definition “operative cylinders” refers, for example, to cylinders of rolling mills for the rolling of metals, those used in paper-mills, those used in oil-pressure applications, shafts of marine motors and in general all cylinders made of metallic and non-metallic materials which are of industrial interest.

BACKGROUND OF THE INVENTION

The grinding of the cylinders described above, and in particular cylinders of rolling-mills or paper-mills, has various drawbacks, associated first of all with the encumbrance and weight of the same which are often considerable.

The latter, in fact, have dimensions varying from 40 mm to 2,300 mm in diameter, 1,000 mm to 12,000 mm in length and weights ranging from a few tens of daN up to 230-250 t.

The function assigned to these cylinders requires that they be processed with a precision and accuracy in the order of a few thousandths of a millimeter.

The grinding machines which can be used for these cylinders therefore have specific characteristics and must not be confused with the smaller and traditional lathes or similar machines which, in this sense, are not capable of effecting these grinding processes.

Known grinding machines normally comprise a piece-holder head, generally fixed, whose function is to entrain the piece being processed in rotation and, in some applications, support it, and a movable tailstock center which can be moved axially with respect to the piece-holder head and whose function is to provide an axial reference with respect to the cylinder and, in some applications, also support it.

The grinding of a cylinder must always be preceded by a preliminary positioning phase of the latter on the machine, which is effected by inserting the cylinder to be ground between the piece-holder head and the tailstock center and subsequently supporting it between centers of the machine associated with the head and tailstock center; furthermore, if necessary, said support of the cylinder is tightened with contrast devices, also called lunettes, which, in some cases, can completely sustain the weight of the cylinder, thus eliminating the supporting function of the head and tailstock center. Either of the solutions is selected in relation to the type of cylinder to be ground and the processing to be effected.

The known art generally envisages that before loading the cylinder, the lunettes be positioned along the base of the machine in order to house the cylinder to be ground. There can be various types of lunettes: those suitable for opposing the grinding forces in the case of cylinders supported on the tips, or suitable for supporting the weight of the cylinder in all other cases. Furthermore, there can be two lunettes for the complete supporting of the cylinder, or at least one when the grinding forces must be opposed; or even no lunette at all in the case of grinding between the centers of squat cylinders, etc. Finally, after the positioning of the lunette has been completed, the tailstock center must be positioned, also in this case in relation to the dimensions of the cylinder. All of these activities and generally all activities aimed at adapting a grinding machine for housing a certain cylinder are defined as the set-up of the machine.

The correct positioning of the cylinder on the grinding machine therefore envisages that the tailstock center and lunettes or contrast devices be positioned in relation to the length of the cylinder at variable distances from the piece-holder head, which is fixed, by moving them in an axial direction either towards or away from the latter, depending on the length of the cylinder.

Both the tailstock center and the lunettes or contrast devices are usually moved and regulated in position individually, regardless of whether these set-up operations are manual or automatic.

In this case, if, on the one hand, the manual solution is economical, on the other, it requires time and accuracy on the part of the operator, whereas although the automatic solution guarantees operational velocity and precision, it requires a movement and control mechanism for the tailstock center and for each of the lunettes.

In the case of manual machines, these problems are even more serious due to the fact that cylinders having different lengths must often be ground consecutively: these set-up operations must therefore be effected for each processing, with considerable time consumption.

In particular, not only must the tailstock center be moved each time, but also the lunettes, as the distances from the piece-holder head (which serves as a reference) must be measured each time and all the lunettes must therefore be moved along the cylinder.

SUMMARY OF THE INVENTION

The general objective of the present invention is consequently to overcome these and other drawbacks of the known art.

This objective is achieved by a grinding machine having the characteristics specified in the first independent claim and the enclosed dependent claims, which should be considered as being an integrant part of the present description.

In order to overcome these drawbacks, a grinding machine for operative cylinders has been conceived which comprises a piece-holder head and a tailstock center provided with centers for the movement and, in some cases, support of a cylinder being processed, wherein the machine comprises movement means associated with both the piece-holder head and the tailstock center and possibly lunettes for allowing them to move along a common movement direction.

According to a further advantageous characteristic of the present invention, both the piece-holder head and the tailstock center and possibly the lunettes are each associated with a single endless screw equipped with two portions having a discordant helicoidal threading, so that they can be moved simply, accurately and rapidly.

BRIEF DESCRIPTION OF THE DRAWINGS

The structural and functional characteristics of the invention, as also its advantages with respect to the known art, will appear more evident form the following description, referring to the enclosed drawings which show a possible practical embodiment of the same invention.

In the drawings:

FIG. 1 illustrates a side view of a grinding machine according to the present invention;

FIG. 2 illustrates a side view in perspective of parts of the machine of FIG. 1;

FIG. 3 illustrates a detail of the machine of the previous figures in a front view;

FIG. 4 illustrates the detail of the previous figure in a side view.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference to FIG. 1, this shows a grinding machine according to the present invention.

The grinding machine 10 comprises a base 11 on which a piece-holder head 13 and tailstock center 12 are translatingly assembled, which serve to move and possibly support a cylinder 14 which is positioned between them during the grinding operation.

More specifically, the machine 10 represented is of the type in which the cylinder being processed is supported by two rotating centers 81 and 83, positioned in the piece-holder head 13 and tailstock center 12, whereas the lunettes 20, 21, 22 are positioned in contact with the cylinder and have the function of providing a contrast to the possible bending of the cylinder caused by the same processing.

It should be pointed out that the machine 10 can equivalently be of a different type, in which the lunettes, in addition to having the function described above, also have the function of supporting the whole weight of the cylinder being processed, whereas the piece-holder head and tailstock center only have the function of bringing it into rotation, to allow its grinding on the part of a grinding wheel or equivalent tool, or said lunettes can be completely absent, as in the case of grinding between the centers of squat cylinders, etc.

The piece-holder head 13 preferably comprises a single body which, in accordance with the disclosures of the present invention, is capable of translating on two linear guides 80 with which it is coupled by means of suitable sliding blocks.

The rotating center 81 which, in some cases, forms a support for the cylinder 14, can be housed inside the body of the piece-holder head 13.

A motor 71, on the other hand, can be possibly positioned in the rear part, with the relative transmission, for actuating the rotation of the cylinder 14.

The tailstock center 12 also comprises a body which is capable of translating thanks to the presence of two linear guides 80 situated in the lower part of the structure with which it is coupled by means of suitable sliding blocks.

The movable center 83, which, in some cases, represents the second support for the cylinder, can be housed inside the body of the tailstock center 12.

Furthermore, if this is required by the processing, as occurs, for example, in the case of the grinding of so-called “thin” cylinders, the tailstock center 12 can have a device in the lower part, which allows a preloading to be generated through a spring device: this preloading acts in an axial direction and guarantees the continuous contact between the cylinder 14 and two movable centers 81 and 83.

The machine 10 can also comprise contrast or supporting lunettes 20, 21, 22.

These, in the embodiment of FIG. 1 can also run on the guides 80 and must be present at least in one unit 20, but generally in at least three 20, 21 and 22 and normally in an odd number. Only in particular cases, when the geometry of the cylinder requires this, is the use envisaged of lunettes in an even number, i.e. without the central lunette. Consequently, except for this particular case, the set of lunettes always comprises a central lunette 20 or, more generally, the central lunette 20 and two side lunettes 21 and 22, or four side lunettes etc.

The machine 10 also comprises a grinding wheel which can be moved parallelly to the axis of the cylinder, not shown for the sake of concision, and in any case known in itself in this type of grinding machine.

Both the piece-holder head 13, and tailstock center 12 and also the lunettes 20, 21 and 22 (if present) can be moved linearly along the base 11 by means of sliding blocks on the linear guides 80 so that they can move towards or away from each other, to house and support cylinders having different lengths.

For this purpose, the grinding machine 10 comprises movement means associated with both the piece-holder head, the tailstock center and also the lunettes or contrast devices, to allow them to move along a common movement direction.

In this example, the movement means comprise a endless screw 16 coupled with both the piece-holder head 13, the tailstock center 12, and lunettes 20, 21 and 22 so that, when brought into rotation, the screw 16 actuates both the approach or withdrawal in the same direction along which the screw 16 extends.

The latter, produced in a single piece, has two threaded portions 160 and 161 with which a corresponding sleeve of the piece-holder head 13, tailstock center 12 and each of the lunettes 20, 21 and 22, is engaged, which will be described in further detail hereunder.

In order to prevent inversions in the rotation sense of the screw 16, the latter is provided with two threaded portions 160, 161 which have discordant have helicoidal threadings, for example an anticlockwise threading and a clockwise threading, preferably having the same pitch.

It should be pointed out that two separate helicoidal screws with a contrasting threading can be equivalently envisaged, instead of a single screw 16, or the latter may not be in a single piece but separable into different sections.

The screw 16 is actuated in rotation by a motor 17, for example an electric brushless motor or the like.

As illustrated more clearly further on, in FIGS. 3 and 4, the movement means also comprise coupling/decoupling means of the piece-holder head 13, tailstock center 12 and lunettes 20, 21 and 22, to the threaded sleeves engaged on the screw 16.

In this way, by acting on the coupling/decoupling means, it is possible, by actuating the screw, to move the head 13, tailstock center 12 and lunettes 20, 21 and 22 in any combination, simply, accurately and rapidly, facilitating the set-up phase of the machine.

This feature easily enables a large quantity of movement combinations of the units 12, 13, 20, 21 and 22, to be obtained, among which the symmetrical movement of the piece-holder head and tailstock center, particularly useful in the case of the grinding of “thin” or “Sendzimir” cylinders, which is described hereunder.

During the positioning of the head 13 and tailstock center 12, these must be moved in the same direction but in opposite senses (to be moved towards the ends of the cylinder). In this way, by actuating the screw 16, the piece-holder head 13 and tailstock center 12 can be moved towards the ends of the cylinder 14 to be coupled with it and support it.

In this way, the cylinder, in spite of its dimensions, can be easily positioned as, once it has been arranged on the machine in the correct position, the head and tailstock center are moved until they are correctly positioned, resting at the ends of the cylinder to be processed.

This particular feature also significantly facilitates the projecting of mechanisms of a possible automatic loading system, as a correct coupling of the head 13 with the cylinder can also be obtained with a simple two-axis loading device (as the head can be moved).

Furthermore, in the case described of the grinding of thin cylinders which require opposition to the grinding forces, it is possible, in the case of odd-numbered lunettes, to keep the central lunette fixed and symmetrically move the outer lunettes; whereas in the case of even-numbered lunettes, both can be equally moved symmetrically.

More generically, there can be various movement conditions of the parts, which should be considered as being an integral part of the method described above, among which the most significant are the following:

1) Symmetrical positioning of the lunettes, piece-holder head and tailstock center with respect to the central reference of the machine: if only the female screw of both lunettes is integral with the screw, they will move for the same distance but in opposite senses, due to the constructive form of the endless screw. Contemporaneously the female screws of the piece-holder head and tailstock center are disengaged from the screw and these two groups consequently remain motionless. After positioning the lunettes, the piece-holder head and tailstock center are positioned by making the female screws of these integral and disengaging those of the lunettes. This positioning procedure can be useful, for example, in the case of the grinding of symmetrical cylinders (for example Sendzimir).

2) Asymmetrical positioning of the piece-holder head and tailstock center—symmetrical positioning of the lunettes: in this case, the lunettes are synchronously positioned, making both of the female screws of the latter integral with the screw. In this way, by actuating the screw, they will move for the same distance but in opposite senses. After positioning these two groups, their female screws are disengaged from the screw. At this point, the female screw of the piece-holder head and tailstock center are alternatingly made integral with the screw, moving first one group and then the other.

3) Asymmetrical positioning of the lunettes, piece-holder head and tailstock center with respect to the center-line of the cylinder: in this case, the groups are positioned, each time making the female screw of one group integral with the screw, whereas the female screws of the other groups not involved in the movement, are disengaged. This procedure can be very useful for moving the above parts in the case of the grinding of asymmetrical cylinders (such as typically hot and cold rolling cylinders), or in applications where the piece-holder head remains fixed such as, in general, all applications except for the grinding of Sendzimir cylinders.

Numerous alternatives to the machine 10 described so far are possible, all considered as being an integral part of the present invention.

The selection mechanism of the parts to be moved envisages, for each of these, a sleeve 90 which comprises a cylindrical mantle and is engaged on the endless screw 16 by means of a threading inside the mantle itself.

Each sleeve 90 can also be connected to the unit to be moved by means of a suitable mechanism.

In principle, it should be noted that, as an alternative to the brake block system described hereunder, in the light of the disclosures provided herein, an expert in the field can also envisage other different solutions; for example, instead of a brake block, the blocking means of the unit to be moved can comprise electromagnets, mechanical coupling means such as fixing pegs, wedges, removable interference profiles or other similar items.

For illustrative and non-limiting purposes, one of these coupling/decoupling means, such as a brake block, is described hereunder.

The coupling/decoupling means of the sleeve to the part to be positioned comprise two arms 91, 92 pivoted to the structure of the part to be moved (piece-holder head, tailstock center and lunette) and each provided with an engagement end 93, 94 with said sleeve 90 and an opposite free end 95, 96 coupled with an actuator 97.

The actuator 97 is preferably a linear actuator, for example a gas, pneumatic, hydraulic, electric actuator or similar: in the non-limited embodiment illustrated, it is a hydraulic actuator equipped with a cylinder and piston which protrudes variably from the cylinder.

The actuator 97 is coupled, preferably hinged, to the free ends 95, 96 of the arms 91, 92; each engagement end 93, 94 of each arm 91, 92 is equipped with a clamp with linings for coupling with the outer cylindrical surface of the sleeve 90.

The two arms 91, 92 have their fulcrum along their body in the points O′ and O′ 1 so as to oscillate, so that as the two free ends 95, 96 approach, the opposite ends 93, 94 move away and vice versa.

The machine 10 preferably comprises a single screw 16 and both the head 13 and the tailstock center 12 and lunettes 20, 21, 22 are equipped with these coupling/decoupling means, each having a specific corresponding sleeve.

In this way, there is a plurality of sleeves along the body of the screw, one for each coupling/decoupling means.

The functioning can be deduced from what has been described so far: when the actuator of one of the coupling/decoupling means is activated to close the linings over the corresponding sleeve, the same part of the machine (head, tailstock center or lunette) can be controlled in translation as a result of the rotation of the screw 16, by activating the latter, in fact, the sleeve, which is prevented from rotating, moves along the screw 16, entraining in translation the element to which the arms are pivoted.

It is therefore possible, with a simple and accurate system, to move head, tailstock center and lunette to position them correctly on the base 11, drastically reducing the set-up times of the machine 10.

Furthermore, in this way, both the lunette and the head and tailstock center can be activated contemporaneously or separately with a single command, obtaining an extremely high versatility of the machine.

Other alternatives can be envisaged, for example, the movement means for the head 13 and for the tailstock center 12 and/or for the lunettes can be produced differently, for example by means of a transmission belt coupled with trolleys, so as to enable the movement of the head 13 and tailstock center 12 and/or lunettes, as envisaged above.

The movement means can equivalently comprise two separate screws and two motors, even if, in this case, the cost of the machine is higher.

A grinding machine 10 as described above can also advantageously be useful for implementing a new positioning method of an operative cylinder.

In short, in the known art, the fact that the piece-holder head is fixed implies a positioning of the cylinder on the machine, which is effected considering the piece-holder head itself as reference, with respect to which all the relevant sizes are measured and the positioning of the cylinder is effected, with negative consequences for both the set-up time of the machine and also for the loading means which must be used in combination with the latter.

These set-up operations in known machines can in fact be effected manually or automatically.

In the former case, this set-up time is extremely important, as a series of different operations are necessary, which must be effected with accuracy in order to verify their correctness. In the latter case, the reduction in the set-up times jeopardizes the simplicity and reliability of the machine, as both the lunettes and tailstock center must be equipped with suitable movement devices and relative control systems.

Another drawback linked with the known art relates to the fact that, during the loading, the cylinder must be moved in three directions and in particular, among these, also along the longitudinal axis, so as to be correctly positioned on the grinding machine; these regulation movements require the use of a loading device.

In manual plants, this device is typically a gantry crane or a jib crane and the precision with which the cylinder must be moved and positioned requires long positioning times, skilled operators and the risk that, with an erroneous manoeuvre, the cylinder, or machine, or both, can be damaged. In automatic plants, the movement of the cylinders is effected with 3-axis loading systems which if, on the one hand, they reduce the maneuvering times and increase the safety of the same, on the other, they require machines which move the load along 3 axes and are consequently, by nature, complex, costly and require maintenance. The positioning of the lunettes and tailstock center is also quite lengthy with the traditional technology, in the sense that they must be moved along the cylinder to be correctly positioned; as far as the lunettes are concerned, for example in the case of the grinding of so-called “thin” or “Sendzimir” cylinders, one is generally positioned in correspondence with center-line of the cylinder and the others at its sides, but care being taken to measure the distances from the side of the cylinder associated with the piece-holder head. Also in this case, if, on the one hand, the manual solution is economical, on the other, it requires time and accuracy on the part of the operator, whereas although the automatic solution guarantees operational velocity and precision, it requires a movement and control mechanism for the tailstock center and for each of the lunettes.

By using the machine 10 according to the present invention, a positioning method can be easily effected, which should also be considered an object of the present invention, which always comprises the following steps:

A—positioning the transversal, longitudinal center-line plane of the cylinder in correspondence with a reference point situated between a movable piece-holder head and a tailstock center of the machine;

B—moving both piece-holder head and tailstock center until they are coupled with the cylinder and supporting it.

A complete version of the positioning method also envisages the following steps:

A1—preparing a rolling cylinder to be ground;

A—positioning the transversal, longitudinal center-line plane of the cylinder in correspondence with a reference point situated between a movable piece-holder head and a tailstock center of the machine;

B—moving both piece-holder head and tailstock center until they are coupled with the cylinder and supporting it;

C—positioning at least two lunettes or contrast devices of said cylinder laterally and at equal distances from said central contrast lunette.

The reference point mentioned in step A above can possibly coincide with the positioning of the transversal, longitudinal center-line plane of the cylinder in correspondence with a fixed lunette with respect to the frame of the machine and/or with respect to the side lunettes.

Numerous variants can obviously be applied to the method described, all object of the present invention; in this sense, some of the steps of the method can be inverted (for example, steps B. and C. can be exchanged) or other steps of the method can be added, relating to secondary regulations of the machine; or the central lunette, due to a particular form and geometry of the cylinder, may not be used.

With reference to step A, the reference point, this is preferably fixed onto the machine and coincides with a lunette or contrast device, in particular with the central lunette; this lunette can obviously be removed to allow the grinding of cylinders having a particular form and geometry.

Both the piece-holder head and tailstock center can preferably be moved so as to be always equidistant from the reference point: their movement, in other words, is of the same entity and is always effected in the same direction but in opposite senses.

Also with respect to the side lunettes, i.e. those situated at the sides of the central lunette which coincides with the reference point, these can be advantageously moved to the same degree and in the same direction, but in opposite senses. There can be one or more of these side lunettes but always in the same quantity on both sides with respect to the central lunette.

In this way, the advantages discussed above are obtained, as the reference point for the whole positioning phase is no longer an end of the cylinder but its center-line, thus overcoming the drawbacks of the known art.

The objectives mentioned in the preamble of the description have therefore been achieved.

The scope of the invention is defined by the following claims. 

The invention claimed is:
 1. A grinding machine for operative cylinders comprising: a piece-holder head; a tailstock center, the piece-holder head and the tailstock center being disposed to have a cylinder positioned to be ground positioned therebetween; and a moving system associated with both the piece-holder head and the tailstock centre to allow them to be moved along a common movement direction.
 2. The grinding machine according to claim 1, further comprising one or more lunettes or contrast devices for the cylinder, suitable for at least supporting said cylinder being processed or to contrast grinding forces, said machine being equipped with a moving system associated with said lunettes to allow said lunettes to move along said common movement direction.
 3. The grinding machine according to claim 1, wherein said moving system comprises an endless screw associated with a base of the grinding machine, said endless screw being having a rotation axis along a parallel direction to said common movement direction and having two portions with a discordant helicoidal threading.
 4. The grinding machine according to claim 3, wherein said moving system further comprises, for each of the two portions having the discordant helicoidal threading of the screw, an internally threaded sleeve engaged on said screw and a coupling/decoupling system of one or more of said piece-holder head, said tailstock, or said lunettes with said internally threaded sleeve.
 5. The grinding machine according to claim 4, wherein said coupling/decoupling system comprises two arms with a fulcrum along a body thereof, each arm having an engagement end with said internally threaded sleeve and an opposite free end coupled with an actuator.
 6. The grinding machine according to claim 5, wherein said actuator is a linear actuator coupled with said free ends of said two arms, and wherein said engagement end of each arm is equipped with a jaw for coupling with an external cylindrical surface of said sleeve.
 7. The grinding machine according to claim 5, wherein said two arms have a fulcrum along their bodies at least at one of said piece-holder head, said tailstock, or said lunettes.
 8. The grinding machine according to claim 7, wherein said piece-holder head, said tailstock and said lunettes are each coupled with a corresponding coupling/decoupling system, a corresponding number of threaded sleeves being engaged on said screw, each of which is configured to be respectively coupled with each coupling/decoupling system.
 9. A positioning method for operative cylinders, for example of rolling-mills or paper-mills, on a grinding machine, the method comprising the following steps: positioning a transversal, longitudinal center-line plane of a cylinder in correspondence with a reference point situated between a movable piece-holder head and a tailstock center of said machine; and moving said piece-holder head and said tailstock center in the direction of said cylinder until there is a reciprocal coupling for one or more of entraining or supporting the cylinder.
 10. A grinding machine according to claim 1, wherein the grinding machine is configured to perform a method according to claim
 9. 11. The grinding machine according to claim 6, wherein said jaw has linings. 